A replaceable brush attachment for an electric toothbrush is known from U.S. Pat. No. 3,369,265. On the brush attachment are bristles in a fixed arrangement. The end of the brush attachment intended for connecting to the handle has a cavity in which provision is made for two opposite lying detent notches, both of which are arranged in the same axial position. A connecting pin of a handle equipped with corresponding detent elevations engages in these detent notches. The end of the brush attachment intended for connecting to the handle is divided by two slots into two legs which are spread apart when the brush attachment is plugged onto the connecting pin, thus permitting a snap-action effect. The end of the connecting pin engages in the end of the cavity, which is conformably shaped in flush fashion.
WO 00 76420 describes an electric toothbrush with a brush attachment. The latter has a coupling means formed by a rubbery component with a sawtooth serration, which frictionally engages over an extension of the housing. A clamping ring is used to achieve high retaining forces without making it difficult to push on the brush attachment. This ring is rotatably held on the brush attachment and equipped with a run-on ramp that grips the housing extension. In addition, provision is made for an anti-rotation device using a coupling sleeve. This solution is relatively elaborate in its construction and hence expensive.
A brush attachment of the prior-art type is known from WO 99 20202. The brush attachment can be plugged onto a handle of an electric toothbrush that has a receiving socket from which a shaft projects. An axial securing element arranged in a brush shank of the brush attachment has a first spring element that is configured like a detent finger and engageable in a groove of the shaft. A second spring element in the form of a bending bar acts on the receiving socket on the handle and is part of a sleeve inserted in the brush shank. This plug-on mechanism is intended for a brush attachment on which a bristle carrier mounted on the brush shank is to be set in oscillatory rotational motion by the shaft of the handle.
It is an object of the present invention to construct a brush attachment of the prior-art type such that it can also be used on a toothbrush with which dental cleaning is supported by a fast vibratory motion of the bristles. The transmission of these vibrations from the handle to the brush attachment should take place without clattering noises in the attachment area, and it should still be easy to plug on and remove the brush attachment. The plug-on mechanism should also display these advantageous characteristics at comparatively high vibration frequencies of preferably 100 to 300 Hz.
This object of the invention is accomplished in that the brush attachment has a plug-on part on which a first and a second spring element are arranged in an axially offset relation to each other and which act on the shaft when the brush attachment is plugged onto the shaft.
This solution enables a connection without play between the shaft and the brush attachment, whereby relatively high forces and torques can be transmitted. The brush attachment is supported on the shaft under bias by in particular elastic shaped elements.
In an advantageous further configuration of the brush attachment of the invention the first and the second spring element are arranged in the same radial position. As a result, the pressure forces of the spring elements act in the same plane, or to be more exact in the same radial direction. This is advantageous with regard to the behavior of the brush attachment when plugged onto the shaft.
According to an advantageous embodiment, provision is made for the first spring element to be constructed as a detent finger that extends axially and engages in an approximately V-shaped detent groove of the shaft. This arrangement can be implemented at very little cost and tells the user of the brush attachment by means of an audible and tangible snap action that the brush attachment is securely seated on the handle.
When, in accordance with an advantageous arrangement, the second spring element is arranged on an area close to the bristle carrier while the first spring element is arranged at a location more remote from the bristles, the second spring element can then act on the free end of the shaft. This means that only the first spring element acts at the beginning of the plug-on operation and very little resistance can be felt when plugging on. The second spring element, which is preferably calculated to have a higher pressure force, does not come into play until at the end.
A preferred arrangement of the detent finger wherein the finger points in the direction of the handle, has the advantage of allowing the detent groove to be deeper and bigger, as the shaft generally has a larger diameter in the vicinity of the handle. The bigger detent groove and the bigger detent finger enable a better snap action to be provided.
A preferred embodiment of the brush attachment of the invention wherein the second spring element is an axially aligned spring bar with a bend curved in the direction of the shaft, whereby the spring bar is arranged between two axial slots of the plug-on part, has the advantage of being an economical and durable solution. A necessary pressure force is assured even after very frequent changing of the brush attachment.
An even better hold is afforded by a third spring element in accordance with another advantageous configuration of the brush attachment of the invention. The third spring element is arranged in an axially offset position relative to the first two spring elements. Conveniently, the plug-on part has several, in particular three, radially offset resilient fingers that urge against the shaft in the mounted state. Through this supporting of the shaft at least three axially offset points the brush attachment is seated particularly quietly and securely on the shaft. The radial support of the plug-on part is also effected preferably at three points of the shaft.
According to another preferred embodiment of the brush attachment of the invention, provision is made for the brush attachment to be constructed for mounting on a shaft having several cross sectional areas, the shaft having an essentially D-shaped cross section at its forward end close to the bristle carrier and a circular cross section at its rear end close to the handle, the forward end of the shaft preferably having a flattening against which a spring element rests. This enables user-friendly attachment and good guidance of the brush attachment. On the one hand, the shaft tip has a small cross section that is inserted in a relatively large receiving opening of the plug-on part. On the other hand, the brush attachment with its bristles has the correct radial alignment. In the first moment of the plug-on movement it is even possible for the bristles to be in any radial alignment. Using a practically automatic rotary movement of the brush attachment in an already partly inserted position, a precise alignment of the bristles is achieved by means of insertion bevels and/or curves running preferably transverse to the shaft on the shaft and/or the plug-on part. The plugging on operation is thus greatly facilitated. Incorrect plugging on is impossible.
When the plug-on part is constructed for mounting on a shaft having at least two circular cross sectional areas of various diameters, with different spring elements resting against the different cross sectional areas, then it is possible for third spring elements, for example, to rest against an enlarged cross sectional area. Preferably provision is made for a first diameter for the first spring element and for a second, bigger diameter for the third spring element. When the brush attachment is pushed on, very little force is required initially because the third spring element does not take support upon the shaft until at the end of the push-on movement. This makes it easy to insert the plug-on part.
It is an advantage for the brush attachment to be encompassed by a soft-elastic padding that extends over at least a section of the brush attachment in order to equip the brush attachment with a shock-absorber function. This padding is preferably arranged in a region proximate the bristles, with a soft-elastic component preferably encompassing a hard part at least in a region opposite the bristles. This shock absorber function enables the forces acting on the teeth on contact with the bristle carrier at high frequencies of vibration to be dampened and reduced. As the result, the user does not experience the contact as bothersome or indeed painful. Drive frequencies can lie above 100 Hz and particularly between 200 and 500 Hz, for example 260 Hz or higher. Without a suitable shock absorbing effect the high acceleration could cause damage to the teeth in extreme cases. It suffices for the padding to extend over a partial area, preferably about half of a circumference and/or only in the vicinity of the brush attachment. In particular, a soft-elastic component additionally covers side areas of the brush attachment in full or in part. The padding can have a structured, in particular studded or ribbed, surface. It is optimal for the soft-elastic component to have a Shore hardness of 30 to 60 A Shore.
An embodiment of a brush attachment of the invention, the present invention itself as well as further advantages thereof will be explained in the following with reference to the description of the accompanying drawing.
In the Figures, like parts are assigned like reference characters.